Essentials for Anchored/Braced Monuments
Need five, straight, 3.5-inch diameter, 40-45 foot long holes
in the ground, one of them oriented vertically,
the other four at angles of 35 degrees from vertical.
The specific issues are:
We have, with one exception, used a compressed-air ``crawler'' drill rig,
designed for drilling shot holes at construction sites (or for open-pit
mines). Other types could be used; the important thing is that the rig
be able to drill into whatever material is present, and be manuverable
(though you can always take more time with a less maneuverable rig).
- The holes
must be straight enough to get 1.25-inch pipe (Schedule 80;
note that 1.25 "pipe" actually measures 1.66" OD)
into them for the full length.
If there is a likelihood of hole wander, the diameter should be increased
above that given above, but it should be kept as small as possible
to minimize the amount of grout needed.
- The intersection of the five pipes should be at a single point
(where the monument will go); this may be at or above
the ground surface, depending on where the mark is wanted.
The drill rig must be able to make small adjustments in hole location
and angle to meet this specification.
The drilling angle can be from 30 to 40 degrees.
Construction Supplies and Materials
The amounts given are for one hole; the total required should thus be
by multiplied by 5.
- Refrigeration insulation, 0.75-inch thick; this
comes in tubes and is taped around item 2
using longitudinal strips of strapping tape.
It is then covered with duct tape.
15-foot length of schedule 40 2.5 inch belled-end PVC pipe.
50 feet of schedule-80 1.25-inch galvanized pipe; this comes in
20-foot sections, which are joined with 1.25-inch schedule-80
(2-inch OD; thin-walled) couplings.
50 feet of 0.5-inch rebar.
Enough grout (cement, sand, and water only - no rock) to completely fill
the hole to the surface.
This should be an expansive grout; regular grout might do
but is not good because it will shrink on drying.
Concrete cannot be used because the rock component makes
it impossible to pour down the pipes.
Centralizer for bottom section of pipe (this is home-made).
Blowout tube for cleaning hole: 60 feet of 1.25-inch schedule-40 PVC
(comes in 20-foot sections, and is assembled, with couplings and PVC
glue on site, used and then discarded).
Fitting to attach to pipe on which antenna can be mounted
Construction Tools and Equipment
This is a partial list of the major tools
and other items needed for construction; some of these
can either be reused, or will be only partly used up.
In addition, a good supply of general-purpose tools (eg. shovels
and hammers) should be available.
Back to Monument introduction
Cement mixer (you do not want to mix this amount of grout by hand
if at all possible).
Compressed air supply with fittings to attach to a blowout tube.
Water for mixing with grout;
Pipe-joint compound, grease, Teflon tape, PVC cement.
Duct tape and strapping tape for attaching insulation around top PVC.
Inclinometer for setting drill angle.
Welding equipment to weld pipes together at intersection; this
takes a few hours at most.